The invention relates to improvements in cutters (also called cutter heads) for gouging ore or rock from mine faces in underground excavations, strip mines, quarries and similar plants. Such cutters can be used in longwall shearing and heading machines to remove coal or rock in mines, in excavations for laying the foundations of buildings and for many other purposes.
It is known to provide a rotary cutter with a support which carries several helically arranged sets of bits serving to penetrate into a rock or ore while the support is caused to rotate and move axially forwardly. The removed material is caused to enter helical grooves, which alternate with the sets of bits, and to flow rearwardly, i.e., counter to the direction of penetration of the cutter into a vein of ore or the like. As a rule, the bits are mounted on helical ribs or threads which are welded to or integral with the peripheral surface of a cylindrical or frustoconical support. Reference may be had to commonly owned German Offenlegungsschrift No. 26 53 706 and to commonly owned U.S. Pat. No. 4,244,626.
The rate at which broken pieces of ore or rock advance in the helical grooves is of great importance because this determines the output of the cutter. The aforementioned prior publications disclose helical grooves each of which is bounded by a cylindrical or frustoconical bottom surface and by two spiral surfaces extending radially of the support. This entails the formation of corners wherein the particles are likely to gather and to stagnate rather than sliding rearwardly counter to the direction of axial movement of the cutter.